Chore: Unit Tests for Individual Filters

[acupofjose]

Chore

Describe the chore

In the process of creating the Not shorthand methods, I've noticed that some of the filter requests are not necessarily being formed correctly. For instance, contains and includes while similar in functionality, require different request formatting.

Per filter tests will be required based off of: http://postgrest.org/en/v7.0.0/api.html#operators

[acupofjose]

Interestingly, attempting to use the contains operator gives me an error:

{
"hint": "No operator matches the given name and argument types. You might need to add explicit type casts.",
"details": null,
"code": "42883",
"message": "operator does not exist: text @> unknown"
}

As though postgrest doesn't know how to use it's own operator?

[elrhomariyounes]

@acupofjose We can close this for now all filters have tests, still to support some types in contains and contained filters as mentioned in #24